Benzene is a highly carcinogenic compound which either is found in or produced during the processing of many hydrocarbon streams. One hydrocarbon substrate or stream in which benzene is found is motor gasoline. In an attempt to reduce pollution from automobile exhaust, environmental regulations have been passed in the United States and in other countries setting limits on the amount of benzene that can exist in motor gasoline in order for the sale of that gasoline to be legal. These regulations can be met only if benzene is removed either from the motor gasoline, itself, or from reformate, which is a major source of the benzene found in motor gasoline.
A typical reformate contains in the range of from about 2-4 wt % benzene in a mixture of paraffins, olefins, naphthenes, toluene, xylenes, ethylbenzene (EB), 9-carbon aromatics (A9s), 10-carbon aromatics (A10s), and other heavy hydrocarbons. Currently, no economically satisfactory technology is capable of directly removing benzene from such a mixture. Existing processes require the use of an expensive benzene heart-cut distillation column, which makes a C6-C7+split of the reformate, producing an overhead stream of 20-30% benzene and 70-80% non-aromatics. The heart-cut benzene stream then must be treated using other known methods, such as adsorption, extraction, etc., to produce high purity benzene or other benzene products.
An economically efficient method is needed for directly removing benzene from hydrocarbon substrates, such as reformate and/or motor gasoline.